Many special telephone services have been made available to subscribers in recent years. Most of these services, such as call waiting and caller identification, are designed to operate within the telephone network as originally designed by American Telephone and Telegraph Company (AT&T) and further developed by the Regional Bell Operating Companies (RBOC) and other telephone service providers. The specific networks currently used by the RBOCs are, in relevant part, identical throughout the United States and most of the developed industrialized world including Western Europe and Japan.
The fundamental architecture of Public Switched Telephone Networks (PSTNs) in the industrialized western world is that separate signaling paths are provided for the voice (or other customer utilized communication circuits) and for information transmitted throughout the network that controls the connection and disconnection of the voice circuits. This is to be contrasted with earlier versions of Public Switched Telephone Networks in which tone signals were transmitted over the same circuits used as voice paths to control set-up and takedown of calls, creation of billing records, and the like.
The current implementation of the control network used in the United States is referred to as the Signaling System 7 (SS7) network. The Advanced Intelligent Network (AIN) is a standard call control protocol which uses the SS7 network for message transport.
The present invention works within the AIN to deliver a special feature not previously disclosed in the art. Therefore, it is advantageous to briefly describe the AIN and its architecture in order to have a complete understanding of the objects and advantages of the present invention. The general architecture of the AIN is relatively simple and is shown in FIG. 1.
FIG. 1 of the specification is a block diagram representing at least part of the AIN of a typical local exchange carrier. While the diagram is simple, the components therein are well known to those skilled in the art. The majority of intelligence in the intelligent switched network resides in computers and switches that embody the AIN, and make use of the SS7 message transport network. SS7 is a network architecture in which information about a telephone call is transmitted over high speed data links that are separate from the voice circuits used to complete the call itself. Using SS7, it is determined whether it is possible to complete a call prior to assigning trunk capacity to set up the voice link. A plurality of central office switches are provided in a typical portion of the public switch telephone network. These are indicated as service switching point (SSP) switches 15-15' in FIG. 1. The dash line between these indicate that the number is arbitrary. Also, non-SSP switches, such as switch 16, are also included within the network.
The difference between an SSP central office switch and a non-SSP central office switch is that the former includes intelligent network functionality. This is an indication that the switch is equipped with appropriate hardware and software so that, when a set of predetermined conditions is detected, the switch will initiate a trigger for a predetermined state of a call on a subscriber line, generate the trigger as an appropriate message to be sent over the AIN, and suspend handling of a call until it receives a reply from the network instructing it to take certain action. In the alternative, the switch will have a default task to execute if a time-out occurs and no response is provided by the network to the query made by the switch. In summary, the SSP switches are those that are fully equipped to deal with and to take advantage of the AIN described herein.
Non-SSP switch 16 is an electronic switch that can generate certain rudimentary packets and provide them over the network, but which must rely on other equipment to provide subscriber lines connected to such a switch with more complex features and services available in the intelligent network. Central offices 15-15' and 16 each have a plurality of subscriber lines commonly designated as 17-17', connected thereto. Typically, the number of subscriber lines will be on the order of 10,000 to 70,000 lines. Each subscriber line 17-17' is connected to a terminating piece of customer's premise equipment that is represented by a like plurality of telephone sets 18-18' for each of the switches.
Interconnecting central office switches 15 and 16 are a plurality of trunk circuits indicated as 19 in FIG. 1. These are the voice path trunks that interconnect the central office and over which calls are connected when established. It should be understood that central office trunking in a typical urban environment is not limited to a daisy chain arrangement implied by FIG. 1. In other words, in a typical network, trunk circuits will exist between central office switch 15' and central office switch 16. Therefore, when a local call is made between two central offices, if a direct trunk connection exists between the offices, and is not busy, the network will assign that trunk to the completion of that particular call. If there is no direct trunking between the two central offices or the direct trunks are all in use, the last call will be routed along trunks from the originating central office to at least one other central office, and through subsequent trunk connections on to the terminating central office.
This general architecture is magnified when a wider geographic area that includes multiple local exchange carriers is considered. In that case, the only significant difference is that certain inter-exchange carrier switches that switch nothing but long distance trunk circuits are included.
Most of the intelligence of the intelligent switched telephone network resides in the remaining components shown on FIG. 1. These are the computers and switches that embody the current version of the common channel interoffice signaling scheme (SS7) mentioned above. Each of switches 15 through 16 is connected to a local signal transfer point (STP) 20 via respective data links 21a, 21b, and 21c. Currently, these data links are 56 kilobit per second bi-directional data links employing a signal protocol referred to as Signaling System 7 (SS7). The SS7 is well known to those skilled in the art and is described in a specification promulgated by the American National Standards Institute (ANSI). The SS7 protocol is a layered protocol wherein each layer provides services for layers above it and relies on the layers below to provide it with services. The protocol employs packets that include the usual beginning and terminating flags and a check bit. Additionally, a signal information field is provided that includes a variable length user specific data field and a routing label. A service information octet is provided that identifies a priority of the message, the national network of the destination of the message, and the user name identifying the entity that created the message. Also, certain control and o sequence numbers are included within the packet, the uses and designations of which are known to those skilled in the art and described in the above-referenced ANSI specification.
All of the SS7 data packets from the switches go to a signal transfer point (STP) 20. Those skilled in the art will recognize that signal transfer point 20 is simply a multi-port, high speed packet switch that is programmed to respond to the routing information in the appropriate layer of the SS7 protocol, and route the packet to its intended destination. The signal transfer point is not normally, per se, the destination of a packet, but merely directs traffic among the other entities on the network that generate and respond to the data packets. It should be noted that signal transfer point devices such as STP 20 are conventionally installed in redundant pairs within a network so that if one device fails, its mate takes over until the first STP is able to return to service. In practice, there are redundant data links between each of central office switches 15-16 for enhanced reliability. For the sake of simplicity of the drawings, the redundant devices have not been illustrated in the drawing figures and the specifications.
Also connected to signal transfer point 20 over SS7 data link 25 is a 1AESS network access point (NAP) 22. Network access point 22 is a computing device programmed to detect trigger conditions. It requires the support of an SSP switch to notify AIN network systems of these trigger detection events. An SSP can support multiple NAP switches. Logically, this SSP is designated as the destination address for many of the packets generated by the network that would otherwise be routed to the 1AESS NAP if it were an SSP equipped switch.
Much of the intelligence, and the basis for many of the new enhanced features of the network reside in the local service control point (SCP) 26 that is connected to signal transfer point 20 via SS7 data link 27. As is known to those skilled in the art, service control points are physically implemented by relatively powerful fault tolerant computers. Typical implementation devices include the Star Service FT Model 3200 or the Star Service FT Model 3300, both sold by American Telephone & Telegraph Company. The architectures of these computers are based on Tandem Integrity S2 and Integrity S1 platforms, respectively. In most implementations of a public switched telephone network, service control points are also provided in redundant mated pairs in order to assure reliability and continued operation of the network.
The computing devices implementing service control points typically accommodate 1 to 27 disk drives ranging from 300 megabytes to 1.2 gigabytes per drive, and have main memory on the order of 24 to 192 megabytes. Thus, it will be appreciated that these are large and powerful computing machines. Among the functions performed by the service control points is maintenance of network data bases used in providing enhanced services. The computer embodying the SCPs can execute at a speed on the order of 17,000,000 instructions per second. Using the SS7 protocol, this translates to about 50-100 transactions (query/response pairs) of network messages per second.
Service control point computers were initially introduced into the network to handle the necessary translations and billing transactions for the implementation of 800 phone service. An 800 number subscriber has at least one dial-up number that is to be called when a call to that subscriber's 800 number is placed. There is no physical central office or area of the country that corresponds to the 800 area code. It is significantly more economical to provide a few central locations at which the look up of the directory number for an 800 number call can be made than to provide the translation information o redundantly at many central office switches. Currently, service control points also include data bases for credit card call transactions.
Also, service control points include data bases that identify particular service customers. In order to keep the processing of data and calls as simple and generic as possible at switches, such as switches 15-15', a relatively small set of triggers are defined at the switches for each call. A trigger in the network is an event associated with a particular subscriber line or call that generates a packet to be sent to a service control point. The trigger causes the service control point to query its data base to determine whether some customized calling feature or enhanced service should be implemented for this particular call, or whether conventional plain dialed-up telephone service should be provided for the call. The results of the data base inquiry are sent back to the switch from SCP 26 through STP 20. The return packet includes instructions to the switch as to how to process the call. The instruction may be to take some special action as a result of a customized calling service or enhanced feature, or may simply be an indication that there is no entry in this data base that indicates that anything other than plain telephone service should be provided for the particular call. In response to receiving the later type message, the switch will move through its call states, select the call digits, and may generate further packets that will be used to set up and route the call, as described hereinabove.
Similar devices for routing calls among various local exchange carriers are provided by regional signal transfer point 28 and regional service control point 29. The regional STP 28 is connected to local STP 20 via an SS7 data link 30. The regional STP 28 is connected to the regional SCP 29 via data link 31 that is physically and functionally the same as data link 27 between the corresponding local devices. As is the case with local devices, regional STPs and SCPs are provided in mated redundant pairs for purposes of reliability.
Both local and regional service control points 26 and 29 are connected via respective data links 35 and 36 to a service management system (SMS) 37. The service management system is also implemented by a large general purpose digital computer and interfaces to business offices in the local exchange carrier and inter-exchange carriers. The service management system downloads information to the data bases of the service control points 26 and 29 when subscribers modify their ensemble of AIN services. Similarly, the service management system downloads, on a non-real time basis, billing information that is needed in order to appropriately invoice telephone company subscribers for the services provided.
The AIN will also include (in the AIN 0.2 software release) service nodes (SNs) such as service node 39 shown in FIG. 1. The AIN 0.2 software release, which incorporates service nodes into the AIN, is known in the art and described in Bell Communications Research GR-1280-CORE "Advanced Intelligent Network (AIN) Service Control Point (SCP) Generic Requirements," Issue 1, August 1993; and Bell Communications Research GR-1298-CORE, "Advanced Intelligent Network (AIN) 0.2 Switching Systems Generic Requirements," Issue 1, November 1993. Those skilled in the art will be familiar with service nodes, which are physically implemented by the same types of computers that embody the service control points 26 and 29. In addition to the computing capability and data base maintenance features, service node 39 also includes voice and DTMF signal recognition devices and voice synthesis devices. Service node 39 is connected to the service management system 37 via a data link 40 that services the service node in essentially the same way it services SCPs 26 and 29. While service node 39 is physically quite similar to SCP 26, there are some important differences in the use to which it is put. Service control points such as SCP 26 normally implement high volume routing services such as call forwarding and 800 number translation and routing. They are also used for maintenance of and providing access to high volume data bases for authorization of billing, such as credit card number validations. In most local exchange carrier networks, service control points are only used for data base lookup and routing services that take place prior to the connection of the call.
By contrast, service nodes, such as service node 39, are used principally when some enhanced feature or service is needed that requires an audio connection to the call or transfer of a significant amount of data to a subscriber over a switch connection during or following a call. As shown in FIG. 1, service node 39 is typically connected to one or more switches via Integrated Service Digital Network (ISDN) links shown as 41. Thus, services that require real-time communication with a customer during a call usually employ the facility of a service node such as service node 39.
The foregoing description is a basic overview, together with a few examples, of the operation of the advanced intelligent network that is a modern public switch telephone system. In summary, the advanced intelligent network is a complex high speed, high traffic volume packet switched messaging arrangement that provides a great deal of versatility in handling of telephone calls. Most network elements, in particular the SSP switches, are designed so that a relatively simple format of a query message is generated upon certain events and the switch will wait for a response from the network before proceeding with call processing. These procedures employ a watchdog timer that will time-out in the event a response to a query is not received.
The present invention relates to a unique feature which is implemented using the AIN to provide a recorded message to a caller who has attempted to call a number which is already busy. The call is later completed when the called line becomes idle. In the past, if a telephone subscriber's line was busy, the network returned an audible busy signal to the caller and terminated further processing of the call. The caller would then have to continue to redial the called number until a call could be completed. Many people may never call back if a busy signal is initially encountered. This could be damaging to a small business that relies upon telephone service as a primary source for its business. Telephone subscribers were not able to hold calls while their telephone lines were in use without the purchase of o additional phone lines or trunk capacity. A disadvantage of using additional phone lines is that calls are completed and then placed on hold.
Some subscribers, predominantly business telephone subscribers, use Automatic Call Distributors (ACD), which are known in the art, to accommodate incoming calls. ACD systems incorporate added trunk capacity for a given number so that multiple calls can be completed to a number without encountering a busy signal. Each call completed to a subscriber using an ACD system can then be placed on hold, if necessary, after completion o to the called party. Many telephone subscribers use ACD equipment to hold calls until the called party is able to talk to the caller. One of the most common users of ACD equipment with phone systems is airline companies. In operation, when calling to make a flight reservation, many callers are informed by a recorded message that an operator will speak to the caller in the order in which the call was received. It is also typical that a recorded message, such as an advertisement or announcement, is played during the time that a caller is waiting to speak to an operator, in the example above to make an airline flight reservation. Although these systems are helpful in providing for connection of calls even during a period of heavy caller traffic, purchasing ACD equipment and adding extra phone lines for a smaller business can be prohibitively expensive and, therefore, not a viable alternative to having its customers encounter busy signals.
As discussed above, use of added phone lines or of ACD or PBX equipment completes the phone call via a chosen trunk line despite the fact that no person will be able to immediately speak with the caller if they are already occupied on another call. This causes inefficient use of trunk lines of the Public Switched Telephone Network (PSTN) during the period that a caller is on hold.
In addition to the added cost of purchasing ACD or PBX equipment or implementing additional phone lines, there is also the problem of system inefficiency. Many business or residential telephone subscribers have peak periods when they receive more calls than in other periods. It is inefficient to have to purchase extra phone lines to accommodate these peak periods when the additional lines are not required outside of those peak periods. For example, a business that sells products through mail may have a peak period immediately following an advertisement for its goods on a television program. This mail order business would have to accommodate its entire system around these peak periods while during the majority of its operating hours, much of its phone line capacity remained unused.
It is also difficult to prioritize the order of responding to incoming calls other than to take the calls in the order in which they were received. In the past, prioritizing certain calls over others has been accomplished by providing separate subscriber numbers and separate trunk rotation sequences. Therefore, without this separate line and rotation, an important customer or call may be placed on hold while other lesser important calls occupy a called party.
Furthermore, local exchange carriers cannot charge a fee or collect any revenue for processing a call that results in a busy condition for which answer supervision is not returned. Therefore, potential revenue is being lost by each local exchange carrier when a called number is busy. Alleviation of the busy condition for callers, even if the call is not completed to the called number immediately, would mean additional revenue to each local exchange carrier. There has been no opportunity in the past to provide a revenue generating enhanced service on a call to a busy line except for call waiting.
Therefore, there is a need for a method of implementing the AIN to allow a called party to place calls in a hold condition without the use of additional phone lines or the purchase of ACD or PBX equipment, to play a recorded message to callers when the called line is occupied and to complete calls placed on hold based upon a priority system established by the called party.